The invention relates in general to the manufacture of synthetic fibers and more particularly to the maintenance of the spinneret plates used in the spinning heads of a textile mill to generate fibers by extrusion through very fine holes therein.
The spinneret plate is the die used for extrusion of polymer forced therethrough. It is made of hard and expensive metal. The holes which can be of any form or size are tooled with precision. In the process the holes tend to be clogged with unprocessed material so that the spinneret plate has to be changed from time to time. The spinneret plate taken away from production is not wasted but cleaned thoroughly before being reused to replace another one. Since there are many spinning heads in a textile mill, the cost of spinneret plates is important. Therefore, the speed and thoroughness of the cleaning operation are an essential part of the manufacturing operation.
The object of the present invention is to provide an improved method and/or apparatus for cleaning the spinneret plates of a textile mill.
When the spinneret plate is to be replaced, the operator is not able to take away from the spinning head only the spinneret plate. In fact, behind the spinneret plate a filtration assembly is always inserted to filter the polymer before it reaches the holes of the die. An outer ring surrounds both the filtration assembly and the spinneret plate for mounting in the spinning head, and all three pieces become a unitary mass when plastic material has set in the holes in the filtration assembly, and at the junction with the outer ring. The unit so formed is known as the spinneret pack. The operator takes away the spinneret pack and replaces it by new and separate parts, namely, a spinneret plate, a filtration assembly and an outer ring which are tight together once mounted within the spinning head.
The general practice in the industry to clean the spinneret plate has consisted of burning away the polymer in an oven in order to disassemble the pack and obtain a spinneret plate which is relatively clean. A further step is required consisting in cleaning the holes of the spinneret plate chemically, e.g. with a solution fluid enough to penetrate the holes. Heat treatment by the oven takes up to eight hours at 800.degree. F. The polymer is burned and smoke with toxic gases evolve which cause air pollution when out of the chimney of the furnace. Ultrasonic cleaning is well known, and its application to workpieces of unusual shape, with recesses and tiny holes is particularly in order. Nevertheless, the only treatment leaves, with the carbonized polymer, residues which necessitate at least an initial cleaning step by a chemical solution before the usual ultrasonic cleaning process can be successfully applied to the spinneret plate. A water and alcohol solution is generally used to condition the spinneret plate. Then, a solvent such as a NaOH caustic solution is able to penetrate the holes and cause the required cavitations therein under the ultrasonic waves. If such a solution is not sufficient, Freon gas is commonly used as solvent because it penetrates most easily into the die holes. Fluorocarbons are useful as final cleaner because they are most effective with a low surface tension, to cavitate within the holes.
Another object of the present invention is to process the spinneret pack from a spinning head without recourse to oven treatment, and to condition the spinneret plate for improved final cleaning thereof.